Cylindrical liner



March 23, 1954 s. s. KlsTLER CYLINDRICAL LINER Filed Nov. 24, 1950 s a 4. A N l l /I /E s a. 4 Z 1 3/m H w I!! l H Hf/ Y H E Z 1 7 /A 12 l \n nuu\\ l 3 E /\Muw\\\\\\\\\\\\ \V VT 1 l l 5\ lll/Wt UN E E jm H 1 40 4 s U 2 s s E 3 2 3 2 U 1 5 2 1 1 1./ u 1 H /s /4 Um. 1 1 1 `/IM M Jv 1 S U 1 5 2 1 1 1 l ZS 37 EE Inverlfor SAMUEL S. K/sTLER' Patented Mar. 23, 1954 UNITED STATES PATENT OFFICE 2,67 3,131- CYLINDRICAL LINER Samuel S. Kistlcr, West Boylston, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application November 24, 1950, Serial No. 197,278 18 Claims. (Cl. SDS-3) l 23 The invention relates to liners for cylinders quite hot, say to about 500 C., and then pushing uch as those of internal combustion engines and of pumps cylinder liner which will very slightly wear piston rings or pistons made of any metal.

Another object of the invention is to provide a refractory liner. Another object of the invention is to provide a liner of some or all of the above characteristics which is nevertheless highly resistant to cracking and spalling.

drawings illustrating many possible embodiments of the mefeatures of this invention,

Figures 1, 2 and 3 are axial sectional views of cylindrical liners inside of metal sleeves,

Figure 4 is an axial sectional View of a bearuse as the bearing for the jour- .Y

the liner I thereinto until 3, When the sleeve 2 cools, it exerts compressive force in radial directions against the liner I because the sleeve 2 shrinks in cooling, and furthermore, the sleeve 2 shrinks in an axial direction as Well as in a radial direction and therefore the ilange 3 is drawn against the end of the liner I and exerts a compressive force on it in an axial direction. I have found that it is desirable to heat the liner I as well as the sleeve 2 in this operation as otherwise there is danger that the liner I will be cracked by thermal shock. 'I'he liner I, being made of ceramic material as hereinafter defined, does notexpand so much as does the sleeve 2 when each of them is heated to the same temperature. Furthermore the sleeve 2 may be heated to a higher temperature for eX- ample C. hotter than the liner I With little danger of cracking the liner I when the latter is introduced into the sleeve.

The liner i is made of essentially crystalline material selected from the group consisting of aluminum oxide A1203, silica Si02, magnesium oxide MgO, and zirconium oxide ZrOg and compounds and mixtures thereof, the hard crystals in the material having a hardness greater than 1000 on the Knoop 100 scale. terials include crystalline alumina, mullite 3A12O3-2Si02, spinel MgO-Al2O3 and zirconia ZrO2 which latter should preferably have from 3% to 6% of lime Ca()l in solid solution in the crystals thereof. Thus other oxides than those practically indistinguishable from zirconia, is calculated as zirconia.

Alumina is the best material now known to me .for the manufacture of the liners I and the most satisfactory process of manufacture now known to me is the cold pressing and subsequent sintering process. I will therefore describe the manufacture of liners out of alumina.

soda NazO therein. This material when crushed it contacts the flange These mavery ne becomes essentially not porous because the pores have disappeared due to the crushing. I take a quantity of this material oi a size known as 900 which means that the particles have an average size of about seven microns but that some of the particles are very small, down to one micron or less and that the material is a mixture of .particle sizes. It is impossible to dene the actual size of the particles but this material is a commercially available material well known to the art and is sufficiently indicated by the above description. I further provide aduantity of clay-like calcium-magnesium silicate such as the mineral hectorite. of the above mentioned crystalline alumina which is a fused alumina and 2% by Weight of the hectorite, I mix such as a kneader or dough mixer with an additional 8% by Weight of a 2 solution o'flrnethyl cellulose in water. Then I screen the mixture throughza' 16 mesh screen andlthematerial is ready' fori. molding.

Imold this material'in'. a rubber lined mold having steel arbor'of` cylindrical shape. The

pressure: is applied by hydraulic iiuid against thefoutside of the'rubber liner. I-prefer a presA surexof'` about5000 pounds per square inch. The pressed'article isxthen removed from the mold and after; drying isV iired under cone conditions. Cone-35,'ring conditions can Abe obtained by heat ingto;a;.top temperature of 1750 C. holding that temperature -for Athree hours.

The outside: surface of this liner l is then ground to anaccurate which4 has been; heated, as above described. Then,uafter the parts havercooled the `inside surthem in any suitable mixer cylindrical surface as by' .meansfof'a'z diamond grinding.- Wheel and then liner Iisf then insertedinto the steel sleeve 2' facergof; the linerI I is. ground perferablywith a'v diamondgrinding Wheelto a smooth and accurate running surface. Bothv cylindrical surfaces-of the sleeve 2 are carefully ground, the inside before assembly andthe outeside after assembly.`

EXAMPLE II Thereis .also available on the' market a calcined but not recrystallizedalumina.known as Bayer process alumina. This -is of high purity, better than 99%` pure, and is the materialfrom which the alumina of Example I is made by fusing in an electric furnace. This calcined. alumina. is made by heating aluminum hy droxide to a temperaturenof about 1000 C.` I take a quantityof this material having low soda content to the amount of` 98% by Weight of the solidportions of the mix, 1%l magnesia, and 1% ci` calcium borosilicate rit. This mixture is then ball-milled wet forsix hours in a porcelain `lined and screened through aiomesh screen.- The resultant powder is then mixed with 51/2% of a y2'70solution of methylcellulose in water and thefmixture is screened through a y16 mesh screen andmolded as described in EXample I preferably at about 5000 pounds persquare inch. The resultant piece isthen dried and red at cone 32 (1700o C. for three hours) after which it is ground and inserted into a steel sleeve 2 as previously described andthenthe interior surface is `ground as specified in EXampleI.

The advantages of a hard liner in an internal combustion engine cylinder include high resistance to Wear. and a low rate at which metal parts in moving. contact with it are worn. The

of. iine calcined mill with flintpebbles, dried Wearing-away of a cylinder wall is largely due to three effects, namely the abrasive action of dust, seizing and tearing of metal surfaces in contact, and corrosion due to condensation of moisture when the cooling Water temperature is below about F. Under ordinary circumstances the hardest material in the dust consists of quartz particles which have ahardnesszof 820 on the Knoop' 100 scale. Therefore ifthe cylinder liners are 1000 or harder, little abrasion will beeiiected. The hardest tool steel has about the hardnessof quartz and is therefore on the lower edge or the acceptable hardness range.

Whenl metals are rubbed over each other, microscopic points-tend to sinter together andptear pieces outfeven-vvith lubrication, and this effect is most pronouncedifthe tivo surfaces are of the same metal, but is also observable when they are different as copper and steel. Cast iron piston rings, therefore, rubbing over a cast iron cylinderv Wall, b'othvwearz it and are Worn' byit.

However, when the cylinder Wall is nonmetallic above substances, there is" forthe surfaces to: or suchtendency isthecoolingl Water circulated inithe jacketsata tempcreaturev belowy 140 F., which means that the `Walls should operate. at substantially` higher temperatures. The water condensedxonitheWalls, in the presence yof'carbon dioxide under pressure and tracesv of vsulfurA dioxide,v is very :corrosiveand may account for alargefracticn of the observed cylinder'wall Wear.

The substances resistant to the attack'of'vvaterl under these conditions andtherefore experience negligible corrosive Wear compared to, cast ironV ori steel. Not only;v do the cylinder walls,` when linedwith the substances listed, not Wear as rapidly as cast iron'or Asteel Walls, kbut asurprising result is the' fact that metal pistons and metaly pistonl rings sliding on. these Walls are than on cast iron or steel. In the case of a sin;Y tered ,aluminalineix the piston rings and piston Woreonly a small-irac'ticn as fastlas lWhenused in castlironor-` steel cylinders. Theiexplanation appears to lie in the reducedttendency for seizure andfscoring to occur and linthe fact thatwhereas a harddust particle can imbed in cast iron' or the softer steels and'thercfore serve as an abradingipoint lfor many excursionsof the piston andV rings," the dust particles beingsofter than the liners reierred to here cannot imbed and are swept away with the'rst stroke of the piston, thus producing very little abrasion ofthe: piston andrings.

"Whilethe strength of. the'materials .listed is not equal to that of-,many metals, I have reduced theimportance ofstrength by shrinking a steel sleeve onto the liner, so'thatall'of the materials are-adequately strong for the purpose. lThese hard substances are very strong in compression but Weak.A in tension so that by applying `a` compressive stress on'the liner, by means ofthe steel sleeve,- so great that at no time during the Work:`

on.` the` Walls of4 listedY above. are' all: highly' Worn very much less I takeadvantage of the` natural .physical properties of; the liner material. and. have achieved. complete success in avoiding.A

upon the design of a particular engine but should be at least 8000 pounds per square inch tangential compression.

If there were no flange .t on the upper end of thesteel sleeve the liner I might expand axially more than the sleeve 2, due to a tempera-- ture gradient between the liner and the sleeve might `result in a crack forming radially through the liner in a plane perpendicular to its axis and approximately one-third of the distance from the top of the liner to the bottom of the piston stroke. This crack would do no harm provided it formed a complete circle and were not a helical crack. In the latter case it would be possible for a piece of the liner to break out.

Referring new to Figure 2, I therefore may provide a liner in two parts Il and il the dividing line 6 being preferably about one-fourth to onethird of the distance from the top of the upper liner to the bottom of the piston stroke. This arrangement eliminates cracking from the cause above noted. This liner 5, 5 is made of any of the materials hereinbefore indicated as suitable materials for the liner I and the parts thereof are preferably formed by sintering as in the case of the liner I. Surrounding the liner c, 5 is a steel sleeve il in compression against the liner 4, 5, as above described in the case of the steel sleeve 2 but this steel sleeve 23 need not have any inwardly extending ange. I find that cast iron or` junction t withoutany deleterious eiects.

However, the differential expansion of the liner and sleeve can be nearly prevented by the use of the flange 3 as represented in Figure 1 and this is the preferred embodiment of my invention. Differential expansion between liner and sleeve is quite variable from one liner material to another due to large differences in coellicient of expansion. For example, aluminum oxide has a coefficient of expansion of about *x10*6 per degree centigrade while that of steel is about lZXIO-'f It will be seen, therefore, that when heat is applied from the inside by the combustion of gases, the liner will be heated up more than the steel sleeve and or may not expand more than the sleeve depending upon the temperature gradient through the Walls and the coefficient of expansion. In the case of .sint-ered aluminum :ride in a motor running at full throttle, the liner expands more than the sleeve. rIluis statement applies to the top end of the liner, and conditions vary from top to bottom due to variable exposure time of the liner to heat S0 that no simple rules can be established. I-Iowever, by combination of the steel ilange and a liner made of two or more sections all operating conditions can be met successfully with the above materials.

Figure 3 illustrates a liner of one of the above described materials in three parts Ill, II and I2 divided at I3 and Id inside of a steel sleeve i5 under compression as indicated and having an inwardly. extending flange it. For many engines, especially `those having large cylinders, this construction will be preferred.

at 2200 n. P. M. and

An unexpected favorable behavior of the liners has been that with continued use the surface roughness decreases although the wear is so small as to be unmeasurable in 600 hours of operation full throttle.

To illustrate the surprising reduction in Wear. on the cast iron piston rings, the data below were obtained comparing a sintered alumina liner with a cast iron liner in a single cylinder air cooled engine operating at 2200 R.. P. M. with full throttle, and driving a dynamometer. In each case the engine was run for 400-6'00 hours with frequent inspection, and the Wear was calculated to an average per hours.

The second column gives the actual loss of weight Table I i Cast Iron, Alumina,

grams percent Similarly, an aluminum alloy piston showed much less wear on a sintered alumina liner according to this invention, but due to the deposition of carbon and the diilculty of precise micrometer measurements the data are not as :reliable and are therefore not given here. The rate of Wear of cast iron cylinder Walls o1' cast iron liners is easily measurable, but we were unable to nd any Wear on the sintered alumina liner according to this invention in 600 hours of operation.

The preferred manner of grinding the liners is to clamp the sleeve 2, 8 or I5, as the case may be, in the chuck of an internal grinding machine, and then to grind a true cylindrical surface on the inside of the liner I or 4, `5 or II), II, I2 as the case may be. This may be done with a suitable internal grinding machine and a diamond grinding wheel is preferably used. A very flne finish and accurate surface can be produced using 'a vitried bonded diamond grinding wheel, but

as the sleeve would expand if it were subjected to the maximum internal pressure expectablein 'the I tE For :example iffthe internal diameter-of the pump liner'is'4".inches;..thei pressure to be pumpedis 1000 pounds per squarel inch,` the sleeve thicknessisf0.` inchlandthemoduluspf elasticity' of the sleeve is 29,000,000 poundsl per square inch such 1:0.0011 inch destructive surgescan occur inliquid..

.this

Since; pumps, good practice would suggest-doubling figure;

If the liner gential compressive stress in the line-rcan be culated from the :equation` has a thickness T, thenthe `tan.- calwhereE"is-the modulus ofela'sticity ofthe liner.

If the liner is 1/8 inchthick and made of sintered alumina with E=50,000,000 pounds per square inch and 1:00022, the compressive stress in the liner will be 14,800 `pounds per square inch, 'a load easily supported.

A pressure of 1000 pounds per square inch is 'what would. be required to pump oil of a density of0.9 out of a well2560 feet deep.

Many pumpsv handling abrasive slurries do not have to operateagainst much pressure. However forpractical `purposes itis desirable to support the liner by a shrinkv interference of at least 0.000lvinchvper inchof diameter, which in the above case would put the liner under a tangential compressive load of2700 pounds perl square inch.

Inanother embodiment the invention is a bearing for a spindle or shaft. Referring now to Fgure 4,.aspindle '20or the grinding` wheelof aY grinding machine has a journal portion 2l having a helical oil groove 22 therein. This spindle 20 is,` of course, made of steel.Y Aportion of the .wheelhead 23 has a cylindricalbore 20 inwhich-is re.-` ceived a steel sleeve25 which is in compression against a liner25 of essentially. crystalline material selected from the group consisting of-alu-v minumoxide, slica,vmagnesium oxide and zirconium oxide vand compounds and mixtures thereof, the .hard crystals in the material havingV a-hardness greater than 1000 onthe Knoop 100 scale. The preferred material is aluminum oxide. which-can be made as described inExamples I and II. The sleeve 25 is shrunk onto the liner 2":3V inthe manner above described. The. compressive stress required depends upon the machine andthe particular kind ofgrinding operation `the machine is to perform, and for many machines and: many grinding operations thiscompressive stress need not be great. For the journalling of shafts inwaftransmission system the compressive stress might `be as low as v100 pounds per square inch. However for external cylindrical grinding maf'- chines of six inch swing and larger theA compressive stress should be atleastv2000 pounds per' square inch -andfmay be greater.

Referringr again to `Figure y4,an.-oil.cl:1annel 30s is .shown in .the wheelhead castingf23 to which oil;

rin the sleeve 25 the oilenters a chamber 33A.

passages 34 in thesleeve which has been ground-ias'.

35 being driven thereto by the groove the ringSv the `oil drains .througha passage L31 mined with a Knoop machine having a 100.gram.

machine the penetrationofathe measure of hardness.v

TableII load.` In the Knoop diamondpoint gives Materials Knoop. Scale Mobs Scale Otlioclase.

Quartz (silica).

Zirconia.

Mullite.-

Spinel.

Topaz.

Garnet.

Zircon.-

CorundumA (alumina).

EXAMPLE III Another example ofthe-manufactured cylindrical liners is as follows: a mixtureof 50 parts I 20 parts of Florida kaol-inand 30 parts of calcined aluminawhich maybe alum-ina, all partsV of calcined kyanite,

Lmlteredand dried thus'producing acake; Thel cake is thenmixed in a suitable mixer, suchas a Simpson type mixer, with 7% of water and'1.%l dextrine basedon the weight of the dried cake. This mix is then molded as described in Example I into tubes which are temperature preferablybetween about 1600o C.

and 1650o C. The resultant liners are thenin-` serted into heated sleevesas above described to make any of the articles herein'described, the two parts'being ground, inside and outside, in the order and in the manner above described.

Kyanite is a natural mineral and like sillimanite and endalusite has the formula Al2O3.SiO2. In

this example sillimanite or andalusite could be. substituted. The resultant product is: substantially mullte 3A12O3-2Si02.

EXAMPLE IV A spinel isV first produced bythe fusion together of stoichiometric proportions o magnesium oxide and aluminum oxide to formMgO.AlzOa.

This is fed: intoa porcelain-lined ball-mill and'.

ilint pebbles and water to an vaverage'- between?, and 10 microns diaming vmixer or the equivalent. 'Ihe finefpowder is molded,` fired, mounted and ground asrn ithecase lof Example III.

to a chamber 3Bl therein and. thence through a passage 391in the wheelhead 23- to any suitable .oil collector or sump whence it is-v of hardness `of at 100 scale may befully dried and red at a- The resultant slip `is ltered, driedand EXAMPLE V setting cement. In order to prevent sagging of The same procedure is followed as in the case this viscous cement during hardening, the liner of Example IV excepting that twice as much alumina as necessary to form the MgO.A12O3 is used. After processing as explained in Example IV the resultant liner is a cubic crystalline spinel carrying the excess alumina in solid solution. Liners made in accordance with this example are harder and more wear-resistant than those made in accordance with Example IV.

EXAMPLE VI I procure a as describ having crystallized from a fusion of zirconium oxide containing ore with calcium oxide as a stabilizing agent, the quantity of calcium oxide being from 3% to 6% of the amount of ZrOz in the ore, the calcium oxide being in solid solution in the zirconium oxide crystals. I ball-mill in a steel ball-mill using steel balls until its average particle is between 3 and 10 microns in diameter. I then treat the slurry with hydrochloric acid to remove the iron, wash it to remove the iron salts and dry it. I mix the resultant powder in a suitable mixer compression. This a rubber lined mold Accordingly for certain uses I have devised other embodiments of the invention which can be made at less expense and which for the purposes intended will readily meet the requirements of practical use. These further embodiments of the invention are illustrated in the following examples.

EXAMPLE VII An alumina liner i having an internal diameter of five and three-quarter inches and having a quarter inch wall was to be fitted into a EXAMPLE VIII A liner four inches in inside diameter by ten a bronze sleeve for pumping salt water into an oil well. outside surface of the alumina liner l was coated a one-quarter inch thick layer of high alumina cement having approximately the chemical formula 3CaO.5Al2Oa. This coated liner was kept moist for 20 days 1n order to permit the cement The liner Was then mounted in a cylindrical grinding machine and ground to 4.750 inches using a sili- Both the sleeve and liner were then placed in an oven and heated to a temperature of 250 C. at which temperature the bronze had expanded enough more than the alumina so that the liner could readily be slipped inside of the sleeve. After cooling the bronze sleeve had with such pressure for the purpose intended.

EXAMPLE IX there is an integral coating of metal on the liner the materials herein specied. problem of creating a perfect cylindrical surface on the liner is thereby greatly simplified. A ve and three-quarters inch diameter liner fteen inches long and one-quarter inch thick made of alumina as specied in Example I was intended fcr use in a diesel engine.

eacvegiei chined vto a smooth inchesin diameter. v-manner described'in cylindrical v surface 6.275

This was assembled inithe Example VllI with a steel Vsleeve having an inside diameter of 6.269 inches using ay temperature ci 400 C. Since many meta-lscan be sprayedythis embodiment is not lim- =ited to copper. Furtherm be 1 formed upon the surface .of any of the materials h fingit with a thin *depositing the metal.

ore a layer of metal can of a liner made out ereinspecied by coatnlm of graphite and electro- Also plastics, such as ethyl cellulose, polyethof the can be sprayed upon liner and there are plastic, inorganic cethe outer surfaces ci liners made ofmaterials herein specined` 11n: the preierred form o i my invention the materialoir the liner is selected from the group consisting ci crystalline alumina, mullite, spinel and- Although l prefer zirconia stabilized Zirconia. with from 3% to 6% of tlierrnal characteristics lime as this has better than unstabilized yzirconia, for many uses such as orbearings unstabilized Zirconia crystallized predominantly in system can be used.

the monoclinic The Word liner has herein been usedto mean the vthe parte i some cases, tomean A'trated for exampw n Figures l,

and il@ and also, in Yentire article as illusand 3 and the Aparts 2F and 20 oFigure Ll. However the context i in each-case indicates in which manner the -Word isused. While in most cases IE prefer a steel -sleeve for the cuterpart a bronze sleeve can be of my cylindrical liner, used in some cases as fin'dicated in Example -VIIL and the sleeve can be'made of other brass or aluminum,

lar'use for'tlie cylindrical liner. 'thefcylindrical liner oi this invention metals such as, for example,

depending upon the particu- In any use of where the internal surface-is a running surface to ce engaged by a reciprocating,

vibrating `metal part, the

rotating, oscillating or liner of the invention will last longer under practically any conditionsmetvvith in practical use. -Whileit is contemplated that oil or'other lubricating material will be supplied to the running surface, 'the liner of the invention will longer withstand use Without oil than will a steel or bronze cylinder orbearing etc., other conditions being equal.

Itv will thus be seen th at -therehas been provided by this invention cylindrical liners for the cylinders of internal pumps and for use as combustion engines and of bearings for spindles and shaftsin which the various objects hereinabove `set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the aboveinvention and as many changes might be `made in the lto be understood that all forth or shown in the ac Yto be interpreted as illustr ing sense.

I claim:

embodiments above forth, it is matterhereinbefore set companying drawing is ative and not in a limit- LVA cylindrical liner assembly comprising an internal cylin-drical liner having a ground internal cylindrical surface, and an external cylinv,drical sleeve made of me against said internal lin tal and in compression least 100 pounds per square inch, said internal liner being essentially non-porous and being -made of essentially crystalline material selected from the group consisting of aluminum oxide, vsilica,-magnesium oxide and zirconium oxideI and 115 scale and there being y20 claim v1 in -which '25 against the internal to the extent of at .70 4sleeve made of metal compounds and mixturessthereof, the hard crys- -tals inthematerial having ahardness greater than 1000 on the Knoop 100 scale.

2. `A cylindrical liner assembly. comprising .an 5 internal cylindrical liner `having a Vground internal cylindrical surface, and an external cylindrical sleeve madeof metal and in compression against said'internal liner to the extent of `at least `lrpoundspersquare inch, said internal l0 liner being essentially non-porous and being made of essentially crystalline material selected 'from the group consisting ofalumina, mullite, spinel and zirconia, said crystalline material having a hardness greater than 1000 on the Knoop 100 no more than of all vmaterial other than said material selected-from the` group consisting of alumina-munite, .spinel `andvzirconiain said internal liner.

3. A cylindrical liner assembly according to the sleeve is in compression against the internal liner to the extentof at least 8000 pounds per square inch.

4. Afcylindrical liner assembly according to 4claim 2 `in which the sleeve is in compression liner to the extent of .at

least 8000 pounds per square inch.

-5. A cylindrical liner assembly comprising an yinternalcylindrical liner having a ground internal cylindrical. surface, and an external cylindrical sleeve made of metaland in'compression against said internal liner to the rextent of at least 100 pounds per square inch, said internal liner being essentially non-porous and being made of crystalline alumina andthere being no more than'10% of all material other than said alumina in said internal liner.

6. lA cylindrical liner assembly comprisingan internal cylindrical liner having a ground internal cylindrical surface, and an external cylin- `drical sleeve made of metal and in compression against said internal liner tothe extent oi at least 8000 pounds-per square inch, said internal liner being essentially non-porous and being made of crystalline alumina and there being no more 4,5 than 10% of allmaterial other than saidv alumina in said internal liner.

'LA cylindrical liner assembly according to claim 1 in whichthe sleeve has a'flange inlenrgagem'entwith one'end of said internal liner and -exerting a compressive force on it in an axial direction.

8. A cylindrical liner assembly vaccording to -claim2 inwhich the sleeve has a flange in -envgagement with one end of. said internal liner and exerting a compressive iorceron it in an axial direction.

9. A cylindrical liner :assembly according to claim 5 inivhich the sleeveihas a flange inengagement With one end of said internal linerrand 'exerting a compressive force on it in an axial direction.

10. A cylindrical liner assembly vaccording to claim `6 invvhich the sleeve'has a flange inengagement with one end of said internalliner and exerting-1a compressive force on it in an axial direction.

11. A cylindrical linerassembly comprising an internal cylindrical liner having a ground internal cylindricalsurace, an external cylindrical and in compression against said internal'liner tothe extent-of atleast 8000 pounds per square inch, lsaid internal liner being vessentially non-porous and being made of` essentially crystalline material selected from the .group .75 v consisting i of aluminum oxidefsilica, magnesium 2,673,131 13 14 oxide and zirconium oxide and compounds and integral exterior with an outer cylindrical surmixtures thereof, the hard crystals in the maface made of metal on said internal liner, and a terial having a hardness greater than 1000 on the metal sleeve outside of and in compression against Knoop 100 scale, and an inwardly extending said exterior with a pressure of at least 100 pounds flange on one end of said sleeve said flange being per square inch.

in engagement with one end of said internal liner 16. A cylindrical liner assembly comprising an and exerting a compi essive force on it in aii axial internal liner made of essentially crystalline madirection. terial selected from the group consisting of 12. A cylindrical liner assembly comprising an alumina, mullite, spinel and zirconia, said crystalinternal cylindrical liner havingagroiind internal line material being essentially non-porous and cylindrical surface, an external cylindrical sleeve having a hardness greater than 1000 on the Knoop made of metal and in compression against said 100 scale and there being no more than 10% internal liner to the extent of at least 8000 of all material other than said material selected pounds per square inch, said internal liner being from the group consisting of alumina, mullite, essentially non-porous and being made of esspinel and zirconia in said internal liner, an

sentially crystalline material selected icrom the integral exterioi with an outer cylindrical surface group consisting of alumina mullite, spinel and made of oiganic plastic material on said internal zirconia, said crystalline material having a hardliner, and a metal sleeve outside of and in comness greater than 1000 on the Knoop 100 scale pression against said exterior with a pressure of and there being no moge than 10% of all ma- 20 atleast 100 pounds per square inch.

terial other than said material selected from the 17. A cylindrical liner assembly comprising an group consisting of alumina, mullite, spinel and internal liner made of essentially crystalline mazirconia in said internal liner, and an inwardly terial selected from the group consisting of extending ilange on one end of said sleeve said alumina mullite, spinel and zirconia, said ciystalilange being in engagement with one end of said line material being essentially non-porous and internal liner and exerting a compressive force having a hardness greater than 1000 on the Knoop on it in an axial direction. 100 scale and there being no more than 10% of 13. A cylindrical liner assembly comprising an all material other than said material selected from internal liner made of essentially crystalline mathe group consisting of alumina, mullite, spinel terial selected from the group consisting of and zirconia in said internal liner, an integral exaluminum oxide, silica, magnesium oxide and zir teiior with an outer cylindrical surface made of conium oxide and compounds and mixtures thereminei al cement on said internal liner, and a metal of, the hard crystals in the material being essleeve outside of and in compression against said sentially non-porous and having a hardness exterior with a pressure of at least pounds greater than 1000 on the Knoop 100 scale, said per square inch. internal liner having a ground internal cylindri- 10. A. cylindrical liner assembly comprising an cal surface, an integral exterior with an outer cyinternal liner made of essentially crystalline malindrical surface made of organic plastic material terial selected from the group consisting of on said internal liner, and a metal sleeve outside alumina, mullite, spinel and zironia, said crystalof and in compression against said exterior with i0 line material being essentially non-porous and a pressure of at least 100 pounds per square inch. having a hardness greater than 1000 on the Knoop A cylindrical linei assembly comprising an 100 scale and there being no more than 10% of internal liner made of essentially crystalline maall material other than said inateral selected from terial selected from the group consisting of alumithe gi oup consisting 0f alumina, mull', SlOIlel num oxide, silica, magnesium oxide and zir- 15 and zirconia in said internal liner, an integral conium oxide and compounds and mixtures thereexterior with an outer cylindrical surface made of, the hard crystals in the material being esof metal on said internal liner, and a metal sleeve sentially non-porous and having a hardness outside of and in compression against said exgreater than 1000 on the Knoop 100 scale, said teri'or with a pressure 0f at least 100 pounds per internal liner having a ground internal cylindri'- square inch.

cal surface, an integral exterior with an outer SAMUEL S. KISTLER. cylindrical surface made of mineral cement on said internal liner, and a metal sleeve outside of Refefences Cited m the me 0f uns patent and in compression against said exterior with a UNITED STATES PATENTS pressure of at least 100 pounds per square inch vi Number Name Date internal liner made of essentially crystalline ma- 1 53511 et al' "A'Illgly terial selected from the group consisting of alumi- 1831411 etz No 10 1931 num oxide, silica magnesium oxide and zircomum 2204626 Scott "June 18 1,940 oxide and compounds and mixtures thereof, the 00 hard crystals in the material being essentially FOREIGN PATENTS non-porous and having a hardness greater than Number Country Date 1000 on the Knoop 100 scale, said internal liner 495,324 Great Britain Nov, 14I 1933 having a ground internal cylindrical surface, an 

